A horse is a horse of course. But Ann Dangerfield owns a horse of a different size: Flying W.F. Royal Blue, a miniature American breed with a name longer than he is.

And don't call him a "pony." He's a "mini," just like the bottles."Inside his head he thinks he's a stallion 16 hands high," says Dale Rickford, who cares for and grooms Royal Blue for horse shows.

Breeding and raising "American minis," in fact, is fast becoming the rage. National Geographic devoted two dozen pages of a recent issue to minihorses. A group of American nuns has taken to raising them to pay for expenses. More and more American families are buying them as pets and keeping them in the backyard with the family dog. They don't eat much, they're not much trouble, and they're good with kids.

"Their popularity has grown an awful lot recently," says Rickford. "I've seen them from $5,000 to $50,000. And I have to say, I find those prices incredible."

Dangerfield has a couple of American minis. The sire of her small white stallion was a national champion and his grandsire also walked off with the honor. Royal Blue's blood is truer blue than his name.

"I like minihorses because they're sturdy," says Dangerfield. "They live into their 20s - like larger horses - and they can be trained to pull carts or do jumps. I wanted something I could handle, so I visited a major breeder and picked out a stallion and a filly. Miniature horses are getting to be the fascination of the horse world."

The history of the breed is "obscured in antiquity," to quote from a popular pamphlet. Basically, the horses were the playthings of royal families in the 1500s. After awhile they began showing up in mines pulling ore carts and doing tricks as part of traveling circuses and gypsy sideshows.

The American Miniature Horse Association was formed in 1978. The horses have to be 34-inches high or less to qualify for membership. Today the breed is known for its excellent temperaments and high intelligence. The horses make better pets than ponies and they also make excellent show animals. Dangerfield plans to cart her two around to shows often.

"When they're handled properly, they develop a fine disposition," says Rickford. "But as with any small animal that serves as a pet, people have a tendency to spoil them."

Adds Dale's wife Terry: "Horse breeders are just now starting to develop activities on the national level for minihorses. But we'll see more. The horses are bright. Ann's little horse, for example, has caught on right away to everything we've asked him to do."

With a little work, in fact, Royal Blue may soon be bringing in the evening paper. Especially the editions with his picture in them.